/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.runtime.util.config.memory;

import org.apache.flink.configuration.ConfigOption;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.configuration.IllegalConfigurationException;
import org.apache.flink.configuration.MemorySize;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Optional;

/**
 * Utilities to fallback to new options from the legacy ones for the backwards compatibility.
 *
 * <p>If {@link LegacyMemoryOptions} are set, they are interpreted as other new memory options for
 * the backwards compatibility.
 */
public class MemoryBackwardsCompatibilityUtils {
    private static final Logger LOG =
            LoggerFactory.getLogger(MemoryBackwardsCompatibilityUtils.class);

    private final LegacyMemoryOptions legacyMemoryOptions;

    public MemoryBackwardsCompatibilityUtils(LegacyMemoryOptions legacyMemoryOptions) {
        this.legacyMemoryOptions = legacyMemoryOptions;
    }

    public Configuration getConfWithLegacyHeapSizeMappedToNewConfigOption(
            Configuration configuration, ConfigOption<MemorySize> configOption) {
        if (configuration.contains(configOption)) {
            return configuration;
        }
        return getLegacyHeapMemoryIfExplicitlyConfigured(configuration)
                .map(
                        legacyHeapSize -> {
                            Configuration copiedConfig = new Configuration(configuration);
                            copiedConfig.set(configOption, legacyHeapSize);
                            LOG.info(
                                    "'{}' is not specified, use the configured deprecated task manager heap value ({}) for it.",
                                    configOption.key(),
                                    legacyHeapSize.toHumanReadableString());
                            return copiedConfig;
                        })
                .orElse(configuration);
    }

    private Optional<MemorySize> getLegacyHeapMemoryIfExplicitlyConfigured(
            Configuration configuration) {
        @SuppressWarnings("CallToSystemGetenv")
        String totalProcessEnv = System.getenv(legacyMemoryOptions.getEnvVar());
        if (totalProcessEnv != null) {
            //noinspection OverlyBroadCatchBlock
            try {
                return Optional.of(MemorySize.parse(totalProcessEnv));
            } catch (Throwable t) {
                throw new IllegalConfigurationException(
                        "Cannot read total process memory size from environment variable value "
                                + totalProcessEnv
                                + '.',
                        t);
            }
        }

        if (configuration.contains(legacyMemoryOptions.getHeap())) {
            return Optional.of(
                    ProcessMemoryUtils.getMemorySizeFromConfig(
                            configuration, legacyMemoryOptions.getHeap()));
        }

        if (configuration.contains(legacyMemoryOptions.getHeapMb())) {
            final long legacyHeapMemoryMB =
                    configuration.getInteger(legacyMemoryOptions.getHeapMb());
            if (legacyHeapMemoryMB < 0) {
                throw new IllegalConfigurationException(
                        "Configured total process memory size ("
                                + legacyHeapMemoryMB
                                + "MB) must not be less than 0.");
            }
            //noinspection MagicNumber
            return Optional.of(new MemorySize(legacyHeapMemoryMB << 20)); // megabytes to bytes;
        }

        return Optional.empty();
    }
}
